Nobody knows. It's a complex champion so it'll take some time to see if he's OP or not. Some champions get hard buffs/nerfs as soon as they hit pbe and then you can predict that they'll be OP or UP, but that hasn't been the case for Aurelion.
EDIT: Apparently he has been slightly nerfed. He might still be strong, but apparently he was on the strong side by release.
Not 100% sure if Riot posted anything about it. I did hear about some last minute changes for the release. Not sure if theose are nerfs or something else.
I assume he will be. As always, riot makes a newly released champion stronger than it should be for whoever can buy it off the bat. After a week or two I assume Aurelion will get a nerf.
EDIT: Apparently he has been slightly nerfed. He might still be strong, but apparently he was on the strong side by release.